1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device, which has a clean contact interface.
2. Description of the Prior Art
According to the decrease of design rule of a semiconductor device, attentions are paid to several problems, including formation of a polymer during fine pattern etching, trouble in discharging the polymer to the atmosphere, increase of resistance due to limitation in the cleaning process, deterioration of reliability of the device due to the resistance increase, etc.
Particularly, a contact etching process for exposing a silicon substrate further requires ohmic characteristics according to high integration of a device. However, in fact, improvement in the integrated degree of a device makes it inevitable to apply a self-aligned contact (SAC) process, which is weak in a view of polymer generation. Further, it becomes more difficult to discharge polymer to the atmosphere according to decrease of contact open area and increase of contact depth. Moreover, formation of the polymer becomes more serious due to limitations of a wet cleaning process and so forth according to compactness of device patterns. As a result, securing ohmic characteristic during the contact etching process is very difficult.
Meanwhile, in an existing semiconductor manufacturing process, an appropriate dry cleaning process or a wet cleaning process is performed during at least a predetermined period of time after the contact etching, in order to maintain cleanness of a substrate in a contact process. This dry or wet cleaning eliminates etching residue and recovers damaged silicon grids.
However, such a dry or wet cleaning cannot provide perfect ohmic contact characteristics although it can maintain cleanness of a substrate in a certain degree.
Therefore, a technique in which a substrate is processed by hydrogen after contact etching has lately been proposed. In the case of post-processing the substrate by hydrogen, the cleaning effect of a contact interface is greatly improved, and thereby ohmic contact characteristics can be secured. Herein, an H2 bake can be given as an example of post-processing by hydrogen.
A method using the H2 bake is very useful from the viewpoint of enabling ohmic contact characteristics to be obtained, but it requires additional apparatuses for the H2 bake, and thereby has a problem in that it is undesirable on the cost side, because additional cost for installation and maintenance of the apparatuses are required.